A celestial light source 10 billion light-years from Earth, thought for several years to be among the brightest sources of radiation in the universe, is really a mirage caused by distortion from the gravity of a nearby galaxy, according to NASA astronomers.

The light source is the most distant known object among the more than 300,000 sources catalogued by the Infrared Astronomical Satellite, an orbiting telescope launched in 1983 by the United States, the Netherlands and the United Kingdom. The light source's distance was later measured in 1991 by British astronomers.

Dr. Peter Eisenhardt and his colleagues at NASA's Jet Propulsion Laboratory, Pasadena, CA, and the California Institute of Technology used the Wide-Field and Planetary Camera 2 onboard the orbiting Hubble Space Telescope to image the source last December.

The source, catalogued as FSC10214+4728, is about 10 billion light-years away, or 5/6ths of the way back to the moment of the Big Bang, the cataclysmic event thought to have been responsible for the creation of the visible universe.

Because of its great distance, it was earlier suggested that the source might be either an extremely luminous, dust-embedded quasar -- or quasi-stellar object -- or a representative of a new class of astronomical object such as a protogalaxy, a galaxy in the process of forming.

The Hubble Space Telescope image studied by Eisenhardt and his colleagues shows the bright source is magnified about 100 times and distorted into the shape of an arc by a "gravitational lens" formed by the nearby galaxy. The galaxy is between Earth and the distant light source. An additional gravitational "counter image," which provides a relatively undistorted view of the original light source, can be seen very faintly beyond the galaxy.

The image shows three objects, descending from upper left to lower right. The faintest object at the upper left is the counter image, or the more accurate representation of the true brightness of the source. The more central object is the galaxy which magnifies the source. The third object at the lower right shows the "arc," or the magnified object.

Even the bright arc is a million times fainter than could be seen by the naked eye. In the Hubble image the brightest source occupies only 7/10th of an arc-second of sky. By comparison, the full Moon occupies 1,800 arc-seconds of sky.

The Hubble Space Telescope's Wide-Field and Planetary Camera 2, which photographed this distant light source, was built by NASA's Jet Propulsion Laboratory and installed in the orbiting Hubble telescope during the telescope's first servicing mission in 1993.

The work was carried out by Eisenhardt and Dr. Michael Werner of JPL, along with colleagues Drs. B. T. Soifer, Gerry Neugebauer, and Lee Armus and graduate student David Hogg of Caltech. The work was supported by the Space Telescope Science Institute in Baltimore, MD, and NASA's Office of Space Science, Washington, D.C.